1. Field of the Invention
This invention relates to filter apparatus such as may be used for the removal of particulate matter from fluids, especially dust-laden air.
2. Description of the Prior Art
In the field of rock drilling, the removal of rock particles from the atmosphere in the vicinity of the rock drill is particularly important in order to maintain the working area atmosphere at a reasonably dust-free level. U.S. Pat. No. 4,277,263, issued July 7, 1981 to W. Bergeron, inventor, describes a hood adapted to surround the drill head and conduit means for removing the dust-laden exhaust and thereafter separating particles from the atmosphere in the exhaust.
Various types of filter elements have been suggested including that illustrated in the above-mentioned U.S. patent.
A filter apparatus normally comprises a chamber having inlet and outlet openings and a filter element located therebetween. The capacity of the filter apparatus expressed in terms of its throughput per unit time, is directly proportional to the surface area of the filter element. In U.S. Pat. No. 1,012,122, issued Dec. 19, 1911 to A. Budil, the filter element is supported on a frame to form a module of relatively high efficiency, which is to say, a high capacity per unit volume. This is effected by forming the filter element as a plurality of individual pockets, each pocket being supported on a pocket frame, the pocket frames being in turn mounted on a main support. The invention relates to improvements in sealing between the individual pockets and the main support.
In U.S. Pat. No. 2,502,560, issued Apr. 4, 1950 to V. Dahlman, a high efficiency filter module comprises a pleated filter element mounted between opposed frame members having complementary intermeshing V-shaped fingers to sandwich opposed sides of the pleated filter element therebetween. This module appears best suited to relatively small units operating at low pressure differentials.
In U.S. Pat. No. 3,622,446, issued Nov. 23, 1971 to P. Burnham, there is shown a disposable self-supporting filter element molded from a phenol thermoset resin containing a high proportion of fibrous materials, the filter element comprising a plurality of integral pockets therein. This element also appears to be best suited for relatively small filter units.
In U.S. Pat. No. 4,129,428, issued Dec. 12, 1978 to R. Andersson et al, a filter module comprises a cloth filter element sewn to provide multiple pockets therein and supported from an external frame. Rigid pocket frames are provided to prevent the pockets from collapsing, but the pocket frames are supported from the pockets rather than the external frame. The means for sealing the filter element to the external frame is, moreover, quite complex.